This study will help to determine the effectiveness of glutamine and creatine as a possible therapy for DMD. Boys with DMD who are enrolled in this trial will be randomly chosen to receive creatine monohydrate or glutamine or an inactive placebo orally for six months. Once a month during the six-month treatment period, the study participants will have their muscle strength evaluated using manual and computerized testing methods. This study will be conducted at several CINRG Centers throughout the U.S., Belgium, Israel and Puerto Rico. This study is supported by the Muscular Dystrophy Association.